The compounds of formula I are described as 8-aza-11,12-secoprostaglandins because of their structural relationship to the naturally occurring prostaglandins.
The prostaglandins constitute a biologically prominent class of naturally occurring, highly functionalized C.sub.20 fatty acids which are anabolized readily in a diverse array of mammalian tissues from three essential fatty acids; namely, 8,11,14-eicosatrienoic acid, 5,8,11,14-eicosatetraenoic acid and 5,8,11,14,17-eicosapentaenoic acid. Each known prostaglandin is a formal derivative of the parent compound, termed "prostanoic acid"; the latter is a C.sub.20 fatty acid covalently bridged between carbons 8 and 12 such as to form a trans, vicinally-substituted cyclopentane in which the carboxy-bearing side chain is "alpha" or below the plane of the ring and the other side chain is "beta" or above the plane of the ring as depicted in formula III: ##SPC1##
The six known primary prostaglandins, PGE.sub.1, PGE.sub.2, PGE.sub.3, PGF.sub.1 .sub..alpha., PGF.sub.2 .sub..alpha., and PGF.sub.3 .sub..alpha., resulting directly from anabolism of the above cited essential fatty acids via the action of prostaglandin synthetase, as well as the three prostaglandis resulting from in vivo dehydration of the PGE's, i.e., PGA.sub.1, PGA.sub.2, and PGA.sub.3, are divided into three groups; namely, the PGE, PGF, and PGA series on the basis of three distinct cyclopentane nuclear sustitution patterns as illustrated as follows: ##SPC2##
It should be noted that the Arabic subscripts designate the number of carbon-carbon double bonds in the designated compound and that the Greek subscript used in the PGF series designates the stereochemistry of the C-9 hydroxyl group.
Although the prostaglandins were discovered independently in the mid-1930's by Goldblatt [J. Chem. Soc. Chem. Ind. Lond., 52, 1056 (1933)] in England and Von Euler [Arch. Exp. Path. Pharmark., 175, 78 (1934)]in Sweden, these complex natural products received little attention from the scientific community until the early 1960's which coincides with the advent of modern instrumentation (e.g., mass spectrometry) which, in turn, was requisite for their successful isolation and structural elucidation by Bergstrom and colleagues [see Angew. Chem. Int. Ed., 4, 410 (1965) and references cited therein for an account of this work]. Within the last decade, a massive international scientific effort has been expended in developing both biosynthetic and chemical routes to the prostaglandins and, subsequently, in investigating of their biological activities. During this period, prostaglandins have been shown to occur extensively in low concentrations in a myriad of mammalian tissues where they are both rapidly anabolized and catabolized and to exhibit a vast spectrum of pharmacological activities including prominent roles in (a) functional hyperemia, (b) the inflammatory response, (c) the central nervous system, (d) transport of water and electrolytes, and (e) regulation of cyclic AMP. Further details concerning the prostaglandins can be found in recent reviews of their chemistry [J. E. Pike, Fortschr. Chem. Org. Naturst., 28, 313 (1970) and G. F. Bundy, A. Rep. in Med. Chem., 7, 157 (1972)], biochemistry [J. W. Hinman, A. Rev. Biochem., 41, 161 (1972)], physiological significance [E. W. Horton, Physiol. Rev., 49, 122 (1969)] and general clinical application [J. W. Hinman, Postgrad. Med. J., 46, 562 (1970)].
The potential application of natural prostaglandins as medicinally useful therapeutic agents in various mammalian disease states is obvious but suffers from three formidable major disadvantages, namely, (a) prostaglandins are known to be rapidly metabolized in vivo in various mammalian tissues to a variety of metabolites which are devoid of the desired original biological activities, (b) the natural prostaglandins are inherently devoid of biological specificity which is requisite for a successful drug, and (c) although limited quantities of prostaglandins are presently produced by both chemical and biochemical processes, their production cost is extremely high; and, consequently, their availability is quite restricted.
Our interest has, therefore, been to synthesize novel compounds structurally related to the natural prostaglandins but with the following unique advantages: (a) simplicity of synthesis leading to low cost of production; (b) specificity of biological activity which may be either of a prostaglandin-mimicking or prostaglandin-antagonizing type; (c) enhanced metabolic stability. The combination of these advantages serves to provide effective, orally and parenterally active therapeutic agents for the treatment of a variety of human and animal diseases. Included are applications in renal, cardiovascular, gastrointestinal, respiratory, and reproductive systems, and in the control of lipid metabolism, inflammation, blood clotting, skin diseases, and certain cancers.
More specifically, in the clinic, prostaglandin agonists can function as agents for improving renal function (e.g., renal vasodilation), antihypertensives, anti-ulcer agents, agents for fertility control, antithrombotics, antiasthmatics, antilipolytics, antineoplastic agents, and agents for the treatment of certain skin diseases.
Prostaglandin antagonists can function as anti-inflammatory agents, anti-diarrheal agents, antipyretics, agents for prevention of premature labor, and agents for the treatment of headache.
The compounds of the present invention are useful as pharmaceutically active compounds. Thus, these compounds are orally active in the treatment of conditions which are responsive to the actions of the natural prostaglandins. It is of course necessary to determine by routine laboratory testing which of the compounds of the present invention are most suitable for a specific end use. Some of the compounds of the invention have prostaglandin-like activity in that they mimic the effect of prostaglandin E.sub.1 in stimulating the formation of cyclic AMP in the mouse ovary in vitro.
The compounds of this invention are particularly useful for improving renal function in that they are renal vasodilators and effect increased renal blood flow in laboratory animals. Certain of the compounds of this invention. e.g., 7-[N-(4-hydroxynonyl)acetamido]heptanoic acid, mimic the effects of prostaglandin E.sub.1 and are useful on oral administration in producing increased renal blood flow (renal vasodilation) in laboratory animals and are useful in improving renal function in animals, e.g., dogs, with poorly-functioning kidneys.
Because of their biological activity and ready accessibility, the compounds of the invention are also useful in that they permit large scale animal testing useful and necessary to understanding of these various disease conditions such as kidney impairment, ulcers, dwarfism caused by poorly-functioning pituitary glands, stroke (thrombus formation) and the like. It will be appreciated that not all of the compounds of this invention have these biological activities to the same degree but the choice of any particular ones for any given purpose will depend upon several factors including the disease state to be treated.
The compounds of this invention can be administered either topically or systemically (i.e., intravenously, subcutaneously, intramuscularly, orally, rectally, or by aerosolization in the form of sterile implants for long action.
Whatever the mode of administration, doses in the range of about 0.10 to 20 milligrams per kiligram of body weight per day are used. The exact dose depends upon the age, weight, and condition of the patient, and the frequency and route of administration.
The low cost and ready accessibility of the compounds of this invention make them particularly promising for applications in veterinary medicine in which field their utilities are comparable to those in human medicine.